In a conventional semiconductor circuit device for obtaining a large current amplifying factor, the D.C. current amplifying factor (or a pulse current amplifying factor) h.sub.FE of a transistor is generally about 50, and it is at most 150 in the case of extremely high current amplification. In a Darlington circuit, which is an amplifying circuit having a forward stage current amplifying transistor Q.sub.1 whose emitter output is directly connected to the base of a succeeding stage power transistor Q.sub.2 , the net amplifying factor becomes the product of the direct current amplifying factors of the individual transistors Q.sub.1 and Q.sub.2. Thus, the overall amplifying factor of the Darlington connection is very large, but since it is a kind of an emitter follower connection (i.e., a connection from which the output is taken from the emitter of the forward stage current amplifying transistor), its input impedance is very large (e.g., several ten K.OMEGA. or larger). Accordingly, the conventional Darlington connection has a shortcoming in that the emitter current of the forward stage transistor Q.sub.1 is small, and the overall direct current amplifying factor is smaller than what is theoretically expected.
In a known effort to mitigate this shortcoming, a resistor R.sub.1 is inserted between the base and the emitter of the succeeding stage transistor Q.sub.2, as shown by broken lines in FIG. 1, so as to increase the collector current of the transistor Q.sub.1 for improving the gain. With this known circuit, however, when the load current is large, saturation of the collector current of the transistor Q.sub.2 cannot be expected. Hence, temperature rise due to the collector loss of the transistor Q.sub.2 becomes high, resulting in the disadvantage that the high temperature rise tends to cause transistor breakdown and that a large load output cannot be produced.